| 年度 | 实际值 |
|---|---|
| 1995 | 21.6 |
| 1996 | 25.2 |
| 1997 | 36.66 |
| 1998 | 24.3 |
| 1999 | 23.7 |
| 2000 | 19.4 |
| 2001 | 19.07 |
| 2002 | 19.53 |
| 2003 | 15.82 |
| 2004 | 16.77 |
| 2005 | 18.32 |
| 2006 | 18.41 |
| 2007 | 18.79 |
| 2008 | 17.41 |
| 2009 | |
| 2010 | 14.52 |
| 2011 | 15.5 |
| 2012 | 14.47 |
| 2013 | 13.42 |
| 2014 | 12.67 |
| 2015 | 10.76 |
| 2016 | 10.33 |
| 2017 | 9.32 |
| 2018 | 10.79 |